The present invention relates to a compressed-air supply installation having a normal operating mode and an idling mode in which the installation consumes less power. Such installations have a compression chamber or chambers connected through one or more inlet valves to a feed line. An installation of this type is disclosed in U.S. Pat. No. 5,101,857 (DE 39 04 172 A1). In normal operation, the inlet valve allows the compression chamber to fill through the feed line but prevents air from returning back to the feed line during and after compression. When the installation is in its idling mode, however, the inlet valve allows air to flow in and out of the compression chamber into and through the feed line.
In U.S. Pat. No. 5,101,857, the inlet valve has a vane that swivels or slides in response to a drive arrangement. This drive arrangement holds the valve vane in an open position while the compressed-air supply installation remains in its idling mode. While the installation delivers no compressed air into the downstream compressed-air actuated installation, it continues to consume some power even in its idling mode. A part of this idling power occurs because the compressor moves an air volume approximating the maximum size of the compression chamber back and forth through the open inlet valve and into and through the feed line. This air movement has associated flow losses that make substantial contributions to the power consumed by the installation in its idling mode.
The flow losses are even greater, and the compressed-air supply installation consumes correspondingly more power while idling, when the air in the feed-line is pre-compressed. This is the case, for example, when the feed line is connected to the inlet line of a supercharged combustion engine downstream of the supercharger (which may be a turbocharger). This arrangement is commonly used in vehicles with supercharged engines. The greater flow losses are caused in these cases by the increased density of the pre-compressed air.
Accordingly, the general object of the present invention is to reduce the power consumption of an idling compressed-air supply installation in a simple way. It is another object of the invention to reduce the idling power consumption when the feed line is connected downstream of a supercharger.